Apparatus for improved power distribution in wirebond semiconductor packages

ABSTRACT

A semiconductor package comprising a die adjacent a substrate, a supporting plate adjacent the die, and a conducting plate abutting the supporting plate and electrically coupled to a metal apparatus adjacent the substrate and the die using a plurality of bond wires. The metal apparatus supplies power to the conducting plate.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 11/557,190 filed Nov. 7, 2006now U.S. Pat. No. 7,534,630, and claims priority from application Ser.No. 10/928,016 filed Aug. 27, 2004 now U.S. Pat. No. 7,151,309, thecontents of which are herein incorporated by reference in its entirety.

BACKGROUND

A wirebond semiconductor package comprises an integrated circuit (“IC”)electrically coupled to a package substrate using bond wires. In turn,the package substrate is electrically coupled to a circuit board usingsolder balls. In this way, multiple electrical connections areestablished between the integrated circuit and the circuit board. An ICin a wirebond package may require access to one or more voltage levels.For example, the IC may require access to voltage sources of 1.1 V, 3.3V, and 5 V, in addition to a ground connection.

To this end, wirebond package substrates comprise multiple metal planes(i.e., layers). Each of these metal planes may carry a different voltagelevel. For example, one metal plane may carry a 3.3 V potential andanother may carry a 0.0 V (i.e., ground) potential. Each of these metalplanes may be electrically coupled to metal rings abutting (e.g.,metallized on) the package substrate and surrounding the IC, called apower ring. Each power ring makes accessible to the IC a voltagepotential found on a metal plane coupled to that power ring. Forexample, the IC may access a 5 V source by way of a power ring that iselectrically coupled to a 5 V metal plane.

The IC accesses the power rings using fine-pitch bond wires. However,because these fine-pitch bond wires are substantially narrow and long,the bond wires carry a considerably high inductance that may compromisesignal integrity. Also, in wirebond packages that do not supportmultiple planes in the substrate, substantially long, narrow metaltraces may be used to carry electrical signals from solder balls to thepower rings. Such long, narrow metal traces also carry substantiallevels of inductance that may negatively impact signal quality. Finally,the power delivery to the core of the die requires long traces from bondpads generally arranged on the die periphery to the core regions of thedie. These traces cause voltage (IR) drops and loss of signal integrity.

SUMMARY

The problems noted above are solved in large part by an apparatus forimproved power distribution in wirebond packages. In an exemplaryembodiment, a semiconductor package comprises a die adjacent asubstrate, a supporting plate adjacent the die, and a conducting plateabutting the supporting plate and electrically coupled to a metalapparatus adjacent the substrate and the die using a plurality of bondwires. The metal apparatus supplies power to the conducting plate.

In another exemplary embodiment, a semiconductor package comprises a dieadjacent a substrate and a conducting plate electrically connected tothe die using at least one of solder bumps or stud bumps. The conductingplate has at least one protrusion exposed through the package moldcompound, wherein the protrusion is adapted to be electrically coupledto a power source using a cable.

In yet another exemplary embodiment, a method of distributing power in apackage comprises electrically coupling a conducting plate to a dieusing at least one of solder bumps or stud bumps, the conducting platecomprising at least one protrusion exposed through the package moldcompound, and electrically coupling the protrusion to a power source ona circuit board using a cable.

In still another exemplary embodiment, a method of distributing power ina semiconductor package comprises electrically coupling a conductingplate to a power source adjacent a substrate, the conducting plateabutting a supporting plate adjacent the substrate, and electricallycoupling the conducting plate to bond pads on a die fixed between thesubstrate and the supporting plate using a plurality of bond wires.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments of the invention,reference will now be made to the accompanying drawings in which:

FIG. 1 shows a cross-sectional side view of a metal apparatuselectrically coupled to a package substrate, in accordance withembodiments of the invention;

FIG. 2 a shows a top-down view of the configuration of FIG. 1, inaccordance with embodiments of the invention;

FIG. 2 b shows a top-down view of a multiple metal apparatuseselectrically coupled to a package substrate, in accordance withembodiments of the invention;

FIG. 3 shows a cross-sectional side view of a cavity-down configurationof the embodiment shown in FIGS. 1 and 2 a, in accordance withembodiments of the invention;

FIG. 4 a shows a cross-sectional side view of a conducting plateabutting a supporting plate, in accordance with embodiments of theinvention;

FIG. 4 b shows a cross-sectional side view of a first conducting plateadjacent a second conducting plate with a supporting substance (e.g.,adhesive) fixed therebetween, and a supporting plate abutting the secondconducting plate, in accordance with embodiments of the invention;

FIG. 5 a shows a package substrate coupled to a metal apparatus havingmultiple protrusions, in accordance with embodiments of the invention;

FIG. 5 b shows a package substrate coupled to a supporting plate and ametal apparatus having multiple protrusions, in accordance withembodiments of the invention; and

FIG. 6 shows a process that may be used to fabricate supporting platesand the metal apparatus, in accordance with embodiments of theinvention.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, companies may refer to a component by different names. Thisdocument does not intend to distinguish between components that differin name but not function. In the following discussion and in the claims,the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . .” Also, in the discussion and in the claims, the term“couple” or “couples” is intended to mean either an indirect or directelectrical connection. Thus, if a first device couples to a seconddevice, that connection may be through a direct electrical connection,or through an indirect electrical connection via other devices andconnections. Further, the terms “annulus” and/or “annular,” as used inall portions of this document including the specification, drawings andclaims, pertain to an enclosed structure that may be any of a variety ofshapes or forms, such as circular, rectangular, triangular, irregular,and so forth. Also, a “conducting plate” as used below may beinterpreted to mean any type of electrically conductive apparatus ordevice. “Adjacent” may be defined as “in relatively close proximity to.”The term “abutting” may be defined as “immediately next to.”

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of theinvention. Although one or more of these embodiments may be preferred,the embodiments disclosed should not be interpreted, or otherwise used,as limiting the scope of the disclosure, including the claims. Inaddition, one skilled in the art will understand that the followingdescription has broad application, and the discussion of any embodimentis meant only to be exemplary of that embodiment, and not intended tointimate that the scope of the disclosure, including the claims, islimited to that embodiment.

Presented herein are various embodiments of a metal apparatus fixedadjacent to a wirebond package IC that may be used to supply voltage tothe IC. Specifically, the metal apparatus may be supplied with a voltage(e.g., 5 V) by coupling the metal apparatus to a package substrate or toa circuit board electrically coupled to the substrate. The metalapparatus may be coupled to the substrate or the circuit board usingmultiple wires and/or cables of substantially larger diameters than thatof fine-pitch bond wires. In turn, the IC may be supplied with thisvoltage by coupling the IC to the metal apparatus. In this way, the ICmay be provided with any of a variety of voltages while preservingsignal integrity.

FIG. 1 shows a cross-sectional side view of a wirebond package 98comprising a substrate 100, solder bumps 102 abutting the substrate 100,a die 104 abutting the substrate 100, a supporting plate 105 abuttingthe die 104, and a conducting plate 103 abutting the supporting plate105. Not all of these structures need be included in all embodiments.For example, in some embodiments, the supporting plate 105 can beomitted. In at least some embodiments, the conducting plate 103 and thesupporting plate 105 may be substantially annular (e.g., rectangular,circular, triangular, irregular) in shape. As mentioned above, theconducting plate 103 may be any electrically conductive apparatus ordevice. The substrate 100 may comprise a power metal plane 106, a powermetal plane 108, vias 110, 140 coupled to the power metal plane 106,vias 112, 142 coupled to the power metal plane 108, a power ring 114coupled to the vias 110, and a power ring 116 coupled to the vias 112.The vias 140, 142 may be electrically coupled to a circuit board 144 byway of the solder bumps 102.

The substrate 100 may further comprise multiple bond fingers 118electrically coupled to at least some of the solder balls 102 by way ofvias 160. The die 104 may comprise multiple die bond pads 120. At leastsome of the bond fingers 118 and the die bond pads 120 may beelectrically coupled using bond wires (not shown), such that electricaldata signals may be transmitted between the die 104 and the substrate100. The conducting plate 103 may be electrically coupled to the powerring 116 using bond wires 124. At least some of the die bond pads 120may be electrically coupled to the conducting plate 103 using bond wires126.

As mentioned above, the die 104 may require at least one voltage supplyto function properly. The circuit board 144 is able to provide such avoltage supply to the die 104. Specifically, the solder balls 102 areelectrically coupled to the circuit board 144. At least a portion of thesolder balls 102 may transfer a voltage required by the die 104 from thecircuit board 144 to the power metal plane 106 by way of the vias 140.In turn, the voltage may be transferred from the metal plane 108 to thepower ring 116 by way of the vias 112 situated therebetween. From thepower ring 116, the voltage may be transferred to the conducting plate103 by way of the multiple bond wires 124. Although not required, in atleast some embodiments, the bond wires 124 may be of a diametersubstantially larger than that of fine-pitch bond wires used in thepackage 98 (e.g., approximately 50 micrometers). The power ring 116 andthe conducting plate 103 preferably are coupled using as many bond wires124 as is reasonably possible. In this way, the total wire inductancegenerated by the collection of bond wires 124 is substantially less thanthat of bond wires otherwise used.

The voltage supplied to the conducting plate 103 may be available to anyportion of the die 104. To provide the voltage of the plate 103 to thedie 104, any number of electrical connections may be established betweenthe plate 103 and die bond pads 120 (i.e., using bond wires 126).Because the die 104 is provided a voltage supply with minimal use ofbond wires and metal traces, the inductive effect caused by wires andmetal traces between the substrate 100 and the die 104 also isminimized. In this way, signal integrity is preserved.

FIG. 2 a shows a top-down view of the configuration of FIG. 1. Inparticular, FIG. 2 a shows the substrate 100 abutting the power rings114, 116, the bond fingers 118 and the die 104. The bond fingers 118 areelectrically coupled to the multiple die bond pads 120 using bond wires122 such that electrical data signals may be transferred therebetween.The die 104 abuts the supporting plate 105 (not visible from a top-downview) and multiple die bond pads 120. The supporting plate 105 abuts theconducting plate 103. As previously discussed, the plate 103 may beelectrically coupled to the power ring 116 by way of multiple bond wires124, wherein each of the bond wires 124 is of a diameter larger thanthat of fine-pitch bond wires used in the package 98. The plate 103preferably is electrically coupled to the power ring 116 using as manybond wires 124 as is reasonably possible of as large a diameter as isreasonably possible, thus minimizing wire inductance. Although theconducting plate 103 is shown to be in the form of an annulus, theconducting plate 103 and the supporting plate 105 may be of any suitableshape and/or may be partitioned in any suitable fashion, per the powerdistribution requirements of the application.

As discussed in context of FIG. 1 above, voltage is provided to variousbond pads 120 of the die 104 from the conducting plate 103. Theconducting plate 103 is supplied with this voltage from the power ring116 by way of multiple, substantially thick bond wires 124. The powerring 116 is supplied with the voltage from the metal plane 108 by way ofthe vias 112. The metal plane 106 is provided with the voltage by thesolder balls 102 by way of the vias 142. The solder bumps 102 areprovided with the voltage from the circuit board 144 coupled to thesolder bumps 102 (not visible from a top-down view).

In the form of an annulus, the conducting plate 103 and the supportingplate 105 expose a core 10 of the die 104. The core 10 comprises asubstantial portion of the circuitry of the die 104. Thus, exposing thecore 10 to the conducting plate 103 as shown in FIG. 2 a allows formultiple electrical connections to be made between the core 10 and theplate 103 without substantial difficulty and with minimal wireinductance effect, thus preserving signal integrity.

FIG. 2 b shows an alternate configuration of the embodiment shown inFIG. 2 a. Specifically, the configuration of FIG. 2 b is substantiallyidentical to that of FIG. 2 a; however, a portion of the conductingplate 103 is detached from the conducting plate 103 to form a separateconducting plate 200. The conducting plate 200 holds a voltage potentialdifferent from that held by the conducting plate 103. For example, theconducting plate 103 may hold a potential of 1.0 V and the conductingplate 200 may hold a potential of 3.3 V. As described above, theconducting plate 103 is supplied with a voltage potential (e.g., 1.0 V)by way of multiple electrical connections to the power ring 116 usingbond wires 124. Similarly, the conducting plate 200 is supplied with avoltage potential (e.g., 3.3 V) by way of multiple electricalconnections to the power ring 114 using bond wires 125. The die 104 mayaccess a 1.0 V supply by way of wirebonds between the conducting plate103 and one or more bond pads 120. Similarly, the die 104 may access an3.3 V supply by way of multiple wirebonds between the conducting plate200 and one or more bond pads 120. In this way, two different voltagelevels are made available to all portions of the die 104. The plates103, 200 preferably are electrically coupled to the power rings 116,114, respectively, using as many substantially-large-diameter bond wires124, 125 as is reasonably possible, thereby minimizing wire inductance.Like the conducting plate 103, the conducting plate 200 may besubstantially annular in shape (e.g., a rectangular, triangular,circular or irregular ring) and may be any electrically conductivedevice or apparatus.

Further separating the conducting plate 103 into multiple, individualconducting plates may provide the die 104 with even more voltage levels.Thus, a die 104 requiring voltages of 1V, 2V, 3V and 4V may be suppliedwith voltages of 1V, 2V, 3V and 4V by four separate conducting plates,each conducting plate supplied with a corresponding voltage by aseparate power ring. Any number of voltage levels may be made availableto the die 104 in this manner. Because the use of metal traces andfine-pitch bond wires is minimized, signal integrity is preserved.

Another exemplary embodiment in shown in FIG. 3. Specifically, FIG. 3shows a cross-sectional side view of a package 298 (e.g., a tape-basedcavity-down package) comprising a cavity-down package substrate 300abutting multiple solder bumps 302, an annular supporting plate 303,multiple bond fingers 306, and power rings 308. A die 304 abuts theannular supporting plate 303 and die bond pads 312. An annularconducting plate 310 abuts the annular supporting plate 303. The annularconducting plate 310 may be any electrically conductive, ring-shapedstructure (e.g., rectangular, circular, irregular, triangular). Part orall of the package 298 may be encapsulated in a mold compound (notshown). The solder bumps 302 are electrically coupled to a circuit board314. Voltage supplies required by the die 304 are available on thecircuit board 314. The solder bumps 302 transfer this voltage from thecircuit board 314 to the power ring(s) 308 by way of a metal traces 316in the substrate 300. A ground connection or some other voltageconnection may be provided to the die 304 by way of a ground plane 317and vias 319. The voltage/ground connections then are routed from thepower rings 308 to the annular conducting plate 310 by way of bond wires318. Once the voltage has been routed to the annular conducting plate310, the die 304 may access the voltage from any of a variety oflocations (i.e., by way of die bond pads 320).

Although only two bond wires 318 are shown, the plate 310 and the rings308 preferably are coupled using as many bond wires 318 as is reasonablypossible. Also, the bond wires 318 may be of a diameter substantiallylarger than that of fine-pitch bond wires used in the package 298. Forthese reasons, the wire inductance effect of the bond wires 318 isminimized. Because the use of metal traces is avoided, and because wireinductance effects are minimized, signal integrity is preserved.

FIG. 4 a illustrates a cross-sectional side view of a supporting plate400 that has been metallized with conducting material to form aconducting plate 402. The supporting plate 400 may be a flexiblematerial or a rigid material that can be metallized by one of any numberof techniques. For example, the supporting plate 400 may be fabricatedusing glass, silicon, plastic, polymer film or some other organicmaterial and the conducting plate 402 may be formed by metallizing thesupporting plate 400 (i.e., using a technique such as sputtering orelectroplating) with a metal such as aluminum or copper or an alloy suchas copper/nickel palladium gold. Other metals also may be used with aperformance similar to that of the aforementioned metals, if appliedwith a sufficient thickness. In some embodiments, as shown in FIG. 4 b,multiple conducting plates 402 may be stacked adjacent each other.Specifically, the configuration of FIG. 4 b is substantially identicalto the configuration of FIG. 4 a; however, an extra conducting plate 404is stacked adjacent the conducting plate 402 with a dielectric adhesivelayer 406 situated therebetween. The conducting plate 404 may be used toprovide an additional voltage level or ground connection to an adjacentdie. Any number of conducting plates may be stacked in this manner. Atleast some of the conducting plates may be electrically-conductive,ring-shaped apparatuses (e.g., rectangular, irregular, triangular,circular, or a combination thereof).

FIGS. 5 a-5 b show yet another exemplary embodiment of the invention.Specifically, FIG. 5 a shows a package 500 that is substantiallyidentical to the package 98 of FIG. 1. However, in FIG. 5 a, thesupporting plate 105 and conducting plate 104 are replaced withconducting plates 502. In some embodiments, the conducting plates 502may be electrically coupled to the die 104 using a plurality of bumpinterconnects 504 (e.g., solder bumps, gold stud bumps). In otherembodiments and as shown in FIG. 5 b, the conducting plates 502 may restabutting supporting plates 501, wherein the supporting plates 501comprise a plurality of vias (not shown) and abut the interconnects 504.Thus, electrical signals may be transferred from the conducting plates502 to the die 104 by way of the vias and the interconnects 504. Anembodiment (e.g., as shown in FIGS. 5 a-5 b) may comprise any number ofconducting plates 502. Because two conducting plates 502 are shown inFIGS. 5 a-5 b, a gap 599 also is shown to identify the separationbetween the plates 502.

In both the embodiments of FIGS. 5 a and 5 b, the conducting plates 502comprise one or more protrusions 506. At least some of the protrusions506 may range in width from approximately tens of microns toapproximately hundreds of microns or more. Preferably, at least some ofthe protrusions 506 may be flush with a mold surface 508 of a mold layer510. Alternatively, one or more of the protrusions 506 may protrudebeyond the mold surface 508. The conducting plate 502 is supplied withvoltage from a circuit board 598 abutting the interconnects 504 by wayof one or more cables 512 coupled to the circuit board 598 and to one ormore protrusions 506. A cable 512 may be a single wire or a multiplewire flexible strip cable. At least some of the cables 512 may have adiameter substantially larger than the diameter of a fine-pitch bondwire used in the package 500 (e.g., approximately 50 micrometers). Inembodiments comprising multiple protrusions 506, the conducting plate502 may be physically divided such that no two protrusions areelectrically coupled to each other, as shown in FIGS. 5 a and 5 b. Inthis way, each protrusion 506 may carry a different voltage level. Thevoltage supplied to each protrusion 506 then is routed through acorresponding portion of the conducting plate 502 and through theinterconnects 504 to the die 104. As in previously describedembodiments, because the use of metal traces and fine-pitch bond wiresis minimized, wire inductance also is minimized and signal integrity ispreserved.

Although FIGS. 5 a and 5 b show the conducting plate 502 coupled to thedie 104 using the interconnects 504, the scope of disclosure is notlimited to this configuration. For example, in at least someembodiments, the conducting plate 502 may provide the die 104 with avoltage supply by way of bond wires (not shown) that may electricallycouple at least some of the protrusions 506 to at least some of the diebond pads 120.

The conducting plates and supporting plates of FIGS. 1, 5 a and 5 b maybe formed using any of a variety of techniques. In embodiments wherein aconducting plate is not coupled to a supporting plate, the conductingplate may be any solid, conducting apparatus and may be formed in anysuitable manner. In embodiments comprising conducting plates withprotrusions (i.e., as in FIGS. 5 a and 5 b), the protrusions may beformed using any appropriate technique or machine. However, inembodiments comprising a conducting plate coupled to a supporting plate,the plates may be fabricated using a metallization process as shown inFIG. 6. The process may begin with the optional fabrication of asupporting plate (block 600). The supporting plate may be made of anyappropriate flexible or rigid material, such as glass, silicon, polymerfilm, plastic or other organic materials. The process may continue bymetallizing the supporting plate with appropriate metal(s) to form aconducting plate (block 602). The plate may be metallized using anysuitable technique, such as sputtering, chemical vapor deposition,electroplating, thermal evaporation, laminating, and so forth. Any of avariety of metals may be used, such as copper or aluminum. Metal alloysor stacks of metals/metal alloys also may be used, such ascopper/aluminum and/or copper/nickel palladium gold. The metallizationtechnique preferably does not damage or degrade the supporting platematerial. The process continues by applying an optional, protectivecoating to the metallized plate (block 604). The coating providesmechanical and chemical protection to the metallized plate. The processcontinues further by optionally forming an aperture in the conductingand supporting plates to form annular plates (block 606). The annularplates may be any suitable shape, such as triangular, irregular,rectangular, circular, and/or a combination thereof. In this way,multiple electrical connections may later be established between theconducting plate and a core of a die adjacent the plates (i.e., as shownin FIGS. 2 a and 2 b). Finally, the process is completed by optionallyforming protrusions in the conducting plate (block 608) as shown inFIGS. 5 a and 5 b. The protrusions may be formed using any suitableprocess, such as an additive process. In embodiments where theplate/protrusions are machined, the protrusions may be formedsubstantially simultaneously with the plates.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. For example, although the subjectmatter above is primarily presented in context of cavity-up laminatepackages, the various embodiments may be implemented in any suitabletype of package, such as tape-based ball-grid array packages andMicroStar® ball-grid array packages. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

1. A method of distributing power in a package, comprising: electricallycoupling a conducting plate to a die using at least one of solder bumpsor stud bumps, said conducting plate comprising at least one protrusionexposed through the package mold compound; and electrically coupling theprotrusion to a power source on a circuit board using a cable.
 2. Themethod of claim 1, wherein using the cable comprises using a cablehaving a diameter greater than that of at least some bond wires used onthe die.
 3. The method of claim 1, wherein electrically coupling theconducting plate to the die comprises using vias in a supporting plate.